International PCT Patent Application No. PCT/AU88/0064 (published as WO 88/06849) describes a method of producing a hollow, totally enclosed, and self supporting food article by the steps of forming a layered material by contiguously positioning two layers of starch and water containing sheets of food material, such that adjacent sheets do not stick together, then cutting the sheets and hereby causing sealing of the interface between adjacent layers continuously around their extremity, and then cooking the shaped food articles in a manner such that steam generated between the layers is of sufficient pressure to force the layers apart in the centre of the article, to create a void in the central area, while retaining contact between the food material sheets of the seal extremities. It would be useful to have a better way of producing the thin sheets required to make these novel food articles.
It has also been found that prior known methods conventionally used in the food industry for rolling a farinaceous dough into a thin sheet are not ideal. These previously known methods when used to produce thin sheets give low manufacturing productivity and product quality, as a result of difficulties that arise in forming a dough using a mixture containing little or no gluten, or if the farinaceous material does contain gluten then problems occur in rolling the sheet to a thickness of less than 1.5 mm because of the stretching and spring back characteristics of the gluten.
In prior art three roll sheeting machines commonly used in the food industry the back pressure in the central region between the rollers is maintained at a relatively low level, and overfeeding of material from the primary roller(s) is compensated for by the excess material being able to flow counter current through the primary roller gap which therefore must be set wide enough for this purpose. In another example of such prior art machines, at least one of the primary rollers is fluted so that excess material is returned back to the feed hopper in the recess of these flutes and by the rotation of the rollers. In some cases the material simply slips on the surface of the primary rollers.
Because only relatively low back pressure is generated in the central region by prior art three roller sheeters the diameters of the secondary rollers have to be such that the nip angle is sufficiently large to create enough drag forces on the material being processed to force it through the final gap between the rollers at the exit.
If rollers of such relatively large diameters are set close enough together to give a thin sheet of farinaceous material in a single pass it has been found that the torque required to drive the rollers become very high and for sheet thickness of less than 1.5 mm the motor power and the mechanical stresses set up are generally in excess of the normal design loads of commonly used sheeters.
For example, U.S. Pat. No. 4,752,493 describes the difficulties that are experienced in attempts to obtain a smooth thin sheet of uniform thickness by rolling a dough prepared from farinaceous materials. In addition, U.S. Pat. Nos. 4,873,093 and 4,834,996 state that starchy materials such as corn flour and potato flour when mixed with water do not from a workable dough that can be used to form sheets of material typically used in the bakery industry.
Other prior art, for example, the preparation of Pita bread and that described in U.S. Pat. Nos. 4,455,321, 4,752,493 and 4,873,093 describe processes for the production of hollow food articles but all of these proceed from a single layer instead on two layers, and/or use chemicals or yeast for leavening gases.